Skeletal structures are formed of bones and adjoining structures which include cartilage, for instance. These skeletal structures may require artificial support or stabilization. For example, the human spine is composed of a column of thirty-three bones, called vertebrae, and their adjoining structures. Most of the vertebrae are capable of individual movement and generally are connected by anterior and posterior longitudinal ligaments. An intervertebral disc is positioned between opposing faces of adjacent vertebrae. Each of these vertebrae include a vertebral body and a dorsal-arch that enclose an opening, called the vertebral foramen, through which the spinal cord and spinal nerves pass. Unfortunately, there are numerous diseases that deteriorate one or more portions of the vertebra or disc. As a result, nerves may be pinched causing enormous pain. In these and other situations, surgical installation of various devices is designed to reduce pain to allow the person to resume a normal life.
One well-known device for spine stabilization procedures is the pedicle screw which is threaded for engagement with bone. A pedicle screw is surgically installed posteriorly into and through a pedicle. A support member such as a plate, semi-rigid member, flexible member, or rigid rod is attached to the pedicle screw for stabilization of the spine. If the threaded portion of the screws do not properly secure to the bone, the pedicle screw will loosen and pull out or break. This loosening can occur over time. Securing the pedicle screw is even more problematic when the bone, particularly cancellous bone, is diseased, deteriorating, or degenerating. For instance, when a pedicle screw is used on osteoporotic patients, the lack of bone density makes it difficult to properly engage the pedicle screw threads within the pedicle resulting in a fragile connection between the pedicle screw and bone.
Therefore, a bone anchor system with improved fixation to bone that does not require screwing into bone and where the external load is dispersed to other load bearing structures in contact with bone is needed.